The present invention relates to valves to dispense products from pressurized containers, and more particularly to aerosol valves for dispensing powders held in suspension in liquified propellants in such containers.
In a conventional form of aerosol valve assembly, a vertically acting aerosol valve is opened to release product in the aerosol container by downwardly depressing a button or cap attached to the top of the upstanding stem of the aerosol valve. When the button is released, the valve is closed by a spring acting on the valve. The valve body positioned at the lower part of the valve stem has an upper horizontal continuous sealing surface circumferentially surrounding the valve stem. This upper horizontal surface, when the aerosol valve is closed, is urged upwardly into sealing relation against the valve sealing gasket by the spring acting on the valve body. One or more orifices in the valve stem are positioned above the lower surface of the valve gasket when the valve is in the closed position. The valve stem passes through a central opening in the gasket, and the circumferential surface of the central opening may provide a radially acting, secondary seal of the valve stem when the valve is closed. When the valve is opened by pressing the button, the valve stem moves downwardly and its one or more orifices will move to a position below the gasket. Product in the aerosol container may now, under the influence of propellant, pass upwardly through the conventional dip tube into the valve housing which surrounds the valve stem and valve body, then upwardly to flow over the upper horizontal surface of the valve body circumferentially surrounding the valve stem, through the one or more orifices into the valve stem, upwardly through the valve stem, and outwardly through an outlet nozzle in the button or cap attached to the top of the valve stem.
The above-described conventional aerosol valve is used to dispense many products including, in aspects particularly relevant to the present invention, products having powder suspended in a liquified propellant. Such products include anti-perspirants, deodorants, foot sprays, etc. Unfortunately, the action of the conventional aerosol valve is compromised by powder build-up on the aforedescribed upper horizontal sealing surface of the valve body when the powder product is released from the aerosol container. This powder accumulation interferes with the full resealing action of the valve by causing the valve to be held partially open after the button is released. The result is that the aerosol container loses pressure even when not in use, and the propellant leakage can impair or destroy the usefulness of the pressurized container after a few operations of the valve. The problem is further exacerbated in the circumstance where modern day high powder loading is desired in the product to be dispensed, for example fifty-sixty percent solids by weight in the case of certain powder antiperspirants where the solids include the powder and other solids in the formulation.
Attempts have been made to overcome the above problems of powder valves, one such instance being disclosed in UK Patent Specification 12166550 wherein a plurality of concentric ribs with sharp top edges are placed on the aforesaid top horizontal sealing surface of the valve body (or on the lower gasket sealing surface) to encircle the valve stem. The sharp top edges cooperate with the gasket to form the valve sealing surfaces, and when powder product is released by actuating the valve, powder build-up is intended to occur inside of, outside of and in the valleys between the concentric ribs rather than at the tops of the ribs. However, powder can still accumulate sufficiently in the valleys to ultimately interfere with the valve sealing action.
A further attempt to overcome the above problems of powder valves is disclosed in U.S. Pat. No. 3,773,064, wherein a circumferential groove surrounds the valve stem with the orifices lying in a conical outwardly tapering section at the top of the groove and the sealing gasket fitting within the groove and around the conical section. A protruding cylindrical ridge in the groove presses into the gasket to enhance sealing. However, the compound surfaces including the bottom of the groove still present opportunities for powder build-up in the design, particularly under present day requirements for powder products having heavy loading of solids.
A still further attempt to overcome the above problems of powder valves is disclosed in U.S. Pat. No. 4,013,197, wherein the valve orifice is in the straight portion of the stem, a groove is positioned below the valve orifice, and a gasket sits partially in and partially out of the groove when the valve is closed to create a primary seal on the straight portion of the stem below the valve orifice and a secondary seal in the groove. The gasket is said to wipe powder from the sealing surfaces on closing of the valve. The design requires excessive stem displacement when depressing the stem to move the valve orifice from above to below the gasket, and excessive gasket deflection since the gasket enters and leaves the groove on opening and closing the valve. Excessive material is also used in the valve body since it requires a wide circumference to accommodate the particular form of groove and gasket. Further, a horizontal annular surface below (or above) the groove on the valve body will accumulate powder to interfere with the secondary seal below the groove.
A successful effort to overcome the above problems of powder valves is disclosed in my prior U.S. Pat. No. 5,975,378 of Nov. 2, 1999, incorporated herein by reference, wherein the conventional upper horizontal sealing surface of the valve body about the valve stem is eliminated. The sealing of the valve is obtained solely in radial directions toward the valve stem by a tight-fitting gasket encircling the valve stem. The outer surface of the valve stem is a straight up and down cylindrical surface having for example two lateral entry orifices, the straight stem surface not including the conventional prior art gasket groove. In the design of this patent, there are no horizontal sealing surfaces and none of the usual groove surfaces where powder can otherwise accumulate to affect the valve sealing function or clog the orifices. The lower valve body is a continuation of the straight valve stem with the exception of a plurality of narrow vertically extending splines spaced about the circumference of the valve body and having large circumferential spaces between each adjacent pair of splines. Each of the plurality of splines tapers inwardly in circumferential direction as the spline nears its upward limit, and the top of each spline forms a minimal horizontal area. When the powder valve is closed, the top of each spline abuts against the sealing gasket to limit the upward return travel of the valve stem under the influence of the valve spring. The minimal horizontal top area of each spline results in a minimum individual and total horizontal surface at the top of the splines, thus preventing powder building up on the tops of the splines to adversely affect the sealing of the valve. The large circumferential spacing between the splines allows powder to fall down between the splines and away from the gasket when the valve is closed, thus preventing any powder build-up on the gasket and stem orifices to interfere with sealing or clogging of the stem orifices.
The present invention also is intended to provide an aerosol powder valve that eliminates the problem of powder build-up interfering with the valve sealing action. The present invention incorporates certain aspects of my prior U.S. Pat. No. 5,975,378, in combination with an alternative stem design having a gasket-retaining stem groove of a particular profile. The present invention is particularly advantageous for dispensing powder products having higher percentages of solid particles.
More specifically, the present invention utilizes the afore-described spline configuration of my prior U.S. Pat. No. 5,975,378 but incorporates thereabove a stem groove extending into and encircling the outer wall of the stem. One or more valve orifices extend through the stem wall into communication with both the stem discharge passage and the stem groove. The valve sealing gasket with its central opening encircles the valve stem and extends into the stem groove. The stem groove is defined, from top to bottom, by an upper annular surface extending downwardly and inwardly from the stem outer surface, a downwardly extending intermediate neck portion, and a lower annular surface extending downwardly and outwardly from the neck portion out to the valve body circumference. The lower downwardly and outwardly extending groove surface extends at a steep angle to the horizontal, and is either a frustoconical surface or preferably a slightly convex surface with a small radius for reasons hereafter discussed. The downwardly extending angle to the horizontal may for example be of the order of fifty degrees, and the convex surface may for example have a radius of curvature of 0.091 inches. These are merely examples, but what is important is that the groove does not have a lower gasket engaging surface that contains or approximates horizontal or concave surfaces so as to accumulate powder during valve operation, leading to leakage between the lower and intermediate groove surfaces and the gasket, and/or to clogging of the valve orifices from the stem groove into the stem discharge passage. Further and importantly, the profile of the lower portion of the stem groove provides a means to remove any powder that may stick to the sharply downwardly and outwardly extending surface. When the powder valve of the present invention is closed the gasket extending into the groove seals against the lower portion of the stem groove. When the powder valve is actuated, the valve stem is depressed and the lower portion of the stem groove accordingly drops below and is spaced from the gasket. The gasket is partially bent away from the stem groove and accordingly no longer seals the valve orifices extending from the groove into the stem discharge passage. As the actuation force is removed from the valve stem, the stem begins to rise under the force of the valve spring. As this occurs, the lower and inner portions of the gasket wipe across the intermediate groove surface and the sharply downwardly and outwardly extending lower groove surface, in a direction to sweep any powder sticking on said surfaces outwardly to the valve body circumference where such powder will fall down between the splines.
Accordingly, the aerosol powder valve of the present invention eliminates any deleterious powder build up, due to both the steep and preferably radiused lower groove surface and the wiping action of the gasket thereacross as the valve is closed from an open position. This holds true through all the successive cycles of operation of the powder valve, thereby resulting in insignificant leakage and optimum usage of propellant and product in the aerosol container.
Other features and advantages of the present invention will be apparent from the following description, drawings and claims.